A complete list of changes are available on the download page as well as in the HISTORY.TXT file that accompanies the install. The complete source code for the 4.4 release is available here: VirtuaWin 4.4 source code.

Did some youtube browsing and found quite a few videos related to VirtuaWin (amazing and fun that people take their time to do this).
Here are two decent ones that explains a bit about the virtual desktop concept as well as a little bit what VirtuaWin is about for the complete beginner on virtual desktops.video 1Video 2
/Johan